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Posts posted by Limberpine

  1. 5 hours ago, billybob said:

    After you answer the last 2 posts above, using the same extension cord from another location, plug into it with the 2 prong DAC only.

    What happens?

    Now plug the amp in by itself.

    What happens?

    If all good after the 2 tests, plug both into extension.


    Okay, so the dac is a 2 prong only plug. So you want me to plug that into the extension cord then do dac to preamp via rca and then preamp to power amp via RCA. Then see what that sounds like and compare it to amp only via extension cord? 

  2. 2 hours ago, babadono said:

    I am trying to help you pinpoint the problem. Trying another amp in the same outlet with the same speakers will determine if its an amp problem or a house wiring problem. But to make things equal you need to short the inputs of each amp when you test. I'm sure your tube amp has a relatively high input impedance, don't know about the SS amp. But shorting the inputs will make the amp under test amplify ground, this is the quietest an amp can be. In this way it equalizes the test of different amps.

    Totally appreciate your help! I just don't know ow what you mean by shorting the inputs. Would that mean, I connect either amp to the speakers with and RCA running out of said amp and then use a screw driver to connect the male end to the shield of the the White RCA plug? 

  3. 7 hours ago, tube fanatic said:

    Two things to try- 1) use an extension cord to plug the amp in someplace else to hear if anything changes.  2) if you have a multimeter, set it to the lowest AC range and clip the leads across the terminals of either speaker and report your reading.




    I used an extension cord and an outlet across the room. No change in noise. 


    I put my multimeter on the ACV 200 setting and the put the red on red and black on black terminals on the speaker and it just read 00.0

  4. 22 minutes ago, babadono said:

    I am not able to play any of your demos of the hum but be that as it may....

    I want to make sure I understand ,the ST70 is just a power amp, correct? Line level unbalanced (RCA) inputs to speaker outputs? When you did the 2 prong/3 prong tests were the inputs open or shorted?

    And do you have any other amp you can plug into the same outlet and same speakers?

    Yes, just a power amp. It has one set of RCA inputs and 5 ways for the speaker connection. 


    When I did both tests, it was merely amp to speakers connected and amp plugged in. Nothing plugged into the rca inputs of the amp. 


    I do have another SS amp I could plug I to the speakers and outlet. Tube wise, I only have another Pre and Phono.  

  5. 48 minutes ago, jimjimbo said:

    That's not a "hum", that's a "buzz" that sounds more like a component failure than anything else.  Both speakers?  Both channels?  All inputs/outputs?

    Yes, both speakers even when its just the power amp hooked to the speakers. Nothing running into it. 

  6. 4 hours ago, henry4841 said:

    One quick question. The sound from the post 10 hours ago, is the sound noticeable from a few feet away or just when you are close to the speaker? Definitely a change in sound from the first sound test you posted. The big Klipsch speaker you have, as I do, will show a hum a 90db speaker would not. The above sound hum is not acceptable. 

    I can certainly hear that same sound that I posted sitting across the room where my chairs are at about 8ft away.

  7. 3 hours ago, jimjimbo said:

    Unbalanced connections are RCA connections if that's what you are confused about.

    Okay, I did the amp, direct to the wall outlet, hooked to the speakers, with nothing running into the amp. I used both the 3 prong and the 2 prong. The sound got louder with the 2 prong. 


    Video attached. 

    • Like 1
  8. 1 hour ago, babadono said:

    All the equipment has 3 prong cords? And un balanced connections? Where does the third wire go on all the equipment? To the chassis and then to the shields of all the un balanced connections?

    DAC is 2 prong cord. Unbalanced connection? I don't understand your last few questions. 

  9. 4 minutes ago, jimjimbo said:


    Thank you. 


    Unplug everything from that power strip other than what is absolutely needed and test.

    Okay, so I will unplug EVERYTHING from the power strip and then plug JUST the power amp into the power strip with the normal 3 prong plug and see what that does. THEN I  will try in the power strip with the 2 prong end to see if anything changes. Is that what you would like me to do? 

  10. 7 hours ago, Dave1290 said:

    Try this just for giggles...  Make SURE your speakers are wired correctly.  Yea, yea I know ya know but check things out and make sure you're good.  NOTHING touching to short anything. 

    I'm running a Prima Luna and using a Schiit Mani from my Linn table.  Sounds fantastic for $150. 

    Double check the speaker wiring for phase and shorts.  Relax and check things out.  Don't stress.  It ain't rocket science.  Go right back to the basics with your set up.  Step at a time.  Start over if you have to and take your time. Cross your fingers too  :)


    I double checked and re seated the speaker wires before turning everything on again. After re wiring connecting the wall outlet problem. 😁

    • Thanks 1
  11. 7 minutes ago, babadono said:

    Neutral and hot were swapped? Those testers don't check for ground/neutral swapped. Was the green "ground light" on even when the wires were swapped?

    Yes, the tester said hot/neu reverse. 


    The Ground light was not on on the power strip before. It now is. 

    • Like 1
  12. 13 minutes ago, billybob said:

    And you plugged 3 prong without adapter into wall and strip after fixing outlet?



    I did and still got the latest noise that I posted just a bit ago. 

    • Like 1
  13. 6 hours ago, billybob said:

    Guess either one.. In just a quick test. Make sure unit power is off first.

    Do both. Do this first before anything further on

    Okay, so I got an outlet tester and it appears the the outlet was wired wrong, so the polarity was switched. I fixed that and it tests correct now. Then I plugged it in like normal into the power strip, still a noise, but different, then I plugged into both the wall and the power strip with the outlet adapter and still a noise, but different.


    Attached is a video of the new noise in the speakers.  

  14. 1 hour ago, henry4841 said:

    Just covering all the bases. Right now it does sound like noisy tube. I think you said it was on both channels. If so it may be a tube that amplifies both channels. In most stereo tube amplifiers there are duplicate tubes for each channel. Is there one tube other than the rectifier that has no mate? If so it could be the culprit. Without seeing a schematic I do not know how your amp is designed. I have seen this problem many times be just a bad connection between the tube and socket. Do try removing each tube and replacing it multiple times. 

    It is in both channels. There are 4 power tubes, and 2 driver tubes that all have mates. I can send you a photo of the amp if you want? I have also reached out to the builder to see what they say too.

  15. 1 hour ago, billybob said:

    Until you do the cheater plug test, you will not have done the test on the ground.


    Yes, I have one of these. So, put this on the end of the amp plug and plug directly into the wall outlet or the power strip? Right now everything is plugged into the power strip.



  16. 4 hours ago, henry4841 said:

    Mech is talking about the power cord. The one you plug into the wall. They sell an adapter for those with old 2 prong wiring in their home for this at most any hardware store. Ground loops are notorious in professional bands when not done properly. One question, is your amplifier and the other equipment plugged into the same AC outlet? If not could be the problem.

    All cords and outlets are 3 prong. Yes, all plugged into the same outlet.

  17. 4 hours ago, MechEngVic said:

    Try bypassing the 3rd prong (ground) of the amp's cord with a cheater plug, see if that makes the hum go away. The ground loop may be between the amp and your A/C power.

    So I did ground the RCA to itself and hum in both speakers. I also took the RCAs off altogether, just speaker wire to amp and there is still a hum. 


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